SyncCalendar/entry/src/main/ets/common/LunarUtil.ets

// entry/src/main/ets/common/LunarUtil.ets
// 公历 → 农历（1901~2099），经典压缩表算法
export class LunarDate {
  year: number = 0;
  month: number = 0;   // 1~12
  day: number = 0;     // 1~30
  isLeap: boolean = false;
}

export class LunarUtil {
  // 农历压缩数据表：每年一个十六进制值（1900~2100）
  private static readonly LUNAR_INFO: number[] = [
    0x04bd8, 0x04ae0, 0x0a570, 0x054d5, 0x0d260, 0x0d950, 0x16554, 0x056a0, 0x09ad0, 0x055d2, // 1900-1909
    0x04ae0, 0x0a5b6, 0x0a4d0, 0x0d250, 0x1d255, 0x0b540, 0x0d6a0, 0x0ada2, 0x095b0, 0x14977, // 1910-1919
    0x04970, 0x0a4b0, 0x0b4b5, 0x06a50, 0x06d40, 0x1ab54, 0x02b60, 0x09570, 0x052f2, 0x04970, // 1920-1929
    0x06566, 0x0d4a0, 0x0ea50, 0x06e95, 0x05ad0, 0x02b60, 0x186e3, 0x092e0, 0x1c8d7, 0x0c950, // 1930-1939
    0x0d4a0, 0x1d8a6, 0x0b550, 0x056a0, 0x1a5b4, 0x025d0, 0x092d0, 0x0d2b2, 0x0a950, 0x0b557, // 1940-1949
    0x06ca0, 0x0b550, 0x15355, 0x04da0, 0x0a5b0, 0x14573, 0x052b0, 0x0a9a8, 0x0e950, 0x06aa0, // 1950-1959
    0x0aea6, 0x0ab50, 0x04b60, 0x0aae4, 0x0a570, 0x05260, 0x0f263, 0x0d950, 0x05b57, 0x056a0, // 1960-1969
    0x096d0, 0x04dd5, 0x04ad0, 0x0a4d0, 0x0d4d4, 0x0d250, 0x0d558, 0x0b540, 0x0b6a0, 0x195a6, // 1970-1979
    0x095b0, 0x049b0, 0x0a974, 0x0a4b0, 0x0b27a, 0x06a50, 0x06d40, 0x0af46, 0x0ab60, 0x09570, // 1980-1989
    0x04af5, 0x04970, 0x064b0, 0x074a3, 0x0ea50, 0x06b58, 0x05ac0, 0x0ab60, 0x096d5, 0x092e0, // 1990-1999
    0x0c960, 0x0d954, 0x0d4a0, 0x0da50, 0x07552, 0x056a0, 0x0abb7, 0x025d0, 0x092d0, 0x0cab5, // 2000-2009
    0x0a950, 0x0b4a0, 0x0baa4, 0x0ad50, 0x055d9, 0x04ba0, 0x0a5b0, 0x15176, 0x052b0, 0x0a930, // 2010-2019
    0x07954, 0x06aa0, 0x0ad50, 0x05b52, 0x04b60, 0x0a6e6, 0x0a4e0, 0x0d260, 0x0ea65, 0x0d530, // 2020-2029
    0x05aa0, 0x076a3, 0x096d0, 0x04afb, 0x04ad0, 0x0a4d0, 0x1d0b6, 0x0d250, 0x0d520, 0x0dd45, // 2030-2039
    0x0b5a0, 0x056d0, 0x055b2, 0x049b0, 0x0a577, 0x0a4b0, 0x0aa50, 0x1b255, 0x06d20, 0x0ada0, // 2040-2049
    0x14b63, 0x09370, 0x049f8, 0x04970, 0x064b0, 0x168a6, 0x0ea50, 0x06b20, 0x1a6c4, 0x0aae0, // 2050-2059
    0x0a2e0, 0x0d2e3, 0x0c960, 0x0d557, 0x0d4a0, 0x0da50, 0x05d55, 0x056a0, 0x0a6d0, 0x055d4, // 2060-2069
    0x052d0, 0x0a9b8, 0x0a950, 0x0b4a0, 0x0b6a6, 0x0ad50, 0x055a0, 0x0aba4, 0x0a5b0, 0x052b0, // 2070-2079
    0x0b273, 0x06930, 0x07337, 0x06aa0, 0x0ad50, 0x14b55, 0x04b60, 0x0a570, 0x054e4, 0x0d160, // 2080-2089
    0x0e968, 0x0d520, 0x0daa0, 0x16aa6, 0x056d0, 0x04ae0, 0x0a9d4, 0x0a2d0, 0x0d150, 0x0f252, // 2090-2099
    0x0d520 // 2100
  ];

  private static readonly MONTH_CN: string[] =
    ['正', '二', '三', '四', '五', '六', '七', '八', '九', '十', '冬', '腊'];
  private static readonly DIGIT_CN: string[] =
    ['一', '二', '三', '四', '五', '六', '七', '八', '九', '十'];

  /** 农历闰月是哪个月（0 表示无闰月） */
  private static leapMonth(y: number): number {
    return LunarUtil.LUNAR_INFO[y - 1900] & 0xf;
  }

  /** 农历闰月天数 */
  private static leapDays(y: number): number {
    if (LunarUtil.leapMonth(y) === 0) {
      return 0;
    }
    return (LunarUtil.LUNAR_INFO[y - 1900] & 0x10000) !== 0 ? 30 : 29;
  }

  /** 农历 y 年 m 月（非闰月）天数 */
  private static monthDays(y: number, m: number): number {
    return (LunarUtil.LUNAR_INFO[y - 1900] & (0x10000 >> m)) !== 0 ? 30 : 29;
  }

  /** 农历 y 年总天数 */
  private static yearDays(y: number): number {
    let sum: number = 348;
    for (let i: number = 0x8000; i > 0x8; i >>= 1) {
      sum += (LunarUtil.LUNAR_INFO[y - 1900] & i) !== 0 ? 1 : 0;
    }
    return sum + LunarUtil.leapDays(y);
  }

  /** 公历毫秒 → 农历日期（超出 1901~2099 返回 null） */
  static lunar(ms: number): LunarDate | null {
    const d = new Date(ms);
    const year: number = d.getFullYear();
    const month: number = d.getMonth() + 1;
    const day: number = d.getDate();
    if (year < 1901 || year > 2099) {
      return null;
    }
    let offset: number =
      Math.floor((Date.UTC(year, month - 1, day) - Date.UTC(1900, 0, 31)) / 86400000);
    let i: number = 1900;
    let temp: number = 0;
    for (i = 1900; i < 2101 && offset > 0; i++) {
      temp = LunarUtil.yearDays(i);
      offset -= temp;
    }
    if (offset < 0) {
      offset += temp;
      i--;
    }
    const leap: number = LunarUtil.leapMonth(i);
    let isLeap: boolean = false;
    let m: number = 1;
    for (m = 1; m < 13 && offset > 0; m++) {
      if (leap > 0 && m === leap + 1 && isLeap === false) {
        --m;
        isLeap = true;
        temp = LunarUtil.leapDays(i);
      } else {
        temp = LunarUtil.monthDays(i, m);
      }
      if (isLeap === true && m === leap + 1) {
        isLeap = false;
      }
      offset -= temp;
    }
    if (offset === 0 && leap > 0 && m === leap + 1) {
      if (isLeap) {
        isLeap = false;
      } else {
        isLeap = true;
        --m;
      }
    }
    if (offset < 0) {
      offset += temp;
      --m;
    }
    const result = new LunarDate();
    result.year = i;
    result.month = m;
    result.day = offset + 1;
    result.isLeap = isLeap;
    return result;
  }

  /** 农历日名称：初一~三十 */
  static dayName(day: number): string {
    const dg: string[] = LunarUtil.DIGIT_CN;
    if (day === 10) {
      return '初十';
    }
    if (day === 20) {
      return '二十';
    }
    if (day === 30) {
      return '三十';
    }
    if (day < 10) {
      return '初' + dg[day - 1];
    }
    if (day < 20) {
      return '十' + dg[day - 11];
    }
    return '廿' + dg[day - 21];
  }

  /** 农历月名称：正月/二月/…/冬月/腊月，闰月带"闰" */
  static monthName(month: number, isLeap: boolean): string {
    const base: string = (month >= 1 && month <= 12) ? LunarUtil.MONTH_CN[month - 1] : '';
    return (isLeap ? '闰' : '') + base + '月';
  }

  /**
   * 日历格子上显示的农历文本：
   * 初一时显示月名（如"九月"），其余显示日名（如"初五"、"十五"）
   */
  static lunarDayText(ms: number): string {
    const info = LunarUtil.lunar(ms);
    if (info === null) {
      return '';
    }
    if (info.day === 1) {
      return LunarUtil.monthName(info.month, info.isLeap);
    }
    return LunarUtil.dayName(info.day);
  }
}